Purification and biochemical characterization of a novel thermoactive fungal pectate lyase from Penicillium occitanis

We purified a novel, thermoactive pectate lyase (Pel), designated Pel1, from the hyperpectinolytic mutant (CT1) of Penicillium occitanis using single-step, anion-exchange chromatography. The purified Pel1 had a pI of 6.5 and a molecular mass of approximately 39 kDa as estimated by SDS-PAGE. The activity of Pel1 was assayed in the presence of several divalent cations at different concentrations. Although we noted that the tested divalent cations are required for maximum activity, we found that none of them could substitute for the effects of 2 mM Ca2+. Using three different carbon sources, our results showed that the highest level of Pel1 activity (434 U/ml) was obtained in a medium supplemented with apple pectin. With polygalacturonic acid, Pel1 exhibited a Km of 0.0199 mg/ml and a Vmax of 17.19 μmol/min/mg at pH 7.0. However, at pH 9.0, the Km and Vmax values were 0.0136 mg/ml and 19.23 μmol/min/mg, respectively. The optimum temperature and pH value required for maximal enzymatic activity were found to be 60 °C and pH 9.0, respectively. At this pH, the half-life time stability at 60 °C was measured to be 16.4 min. The novel Pel1 is very thermally stable and presents alkalophilic parameters; such features are rarely exhibited by fungal Pels.